ci: improve history assertion capabilities and add history assertions

[anthonyting]

Issue #, if available:

#261

Description of changes:

This set of changes supports history assertions, and adds the assertions for tests that required some changes in logic.

Changes:

• Support generating history files when calling assertEventSignature with no existing history files
• Add support for invocationCompletedDifference setting in history assertion since, depending on checkpoint latency, a test may complete within a different number of invocations
• Updating tests to generate more consistent results
  • Wait for submitted callback instead of just started callback to ensure invocations complete
  • Combine unnecessary separated test blocks where the setup is the same in both tests
  • Enable some skipped/disabled tests
• Updating README for adding examples
  • Include information about history assertions
  • Update testHelper interface

Next:

• Add the rest of the history assertions which don't require any logic changes.

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